Alligator teeth are not that different from ours!
Crocodiles exhibit the same complex dental architecture and morphological characteristics as mammals such as thecodont teeth (teeth that are embedded in sockets). They also have a secondary palate like that of the mammals. In addition, unlike humans, they have the capability of renewing their teeth many times within their lifetime. Thus the alligators can be considered a classic model to be used in tooth regeneration studies.
One crocodile tooth renews about 50 times
Crocodiles are polyphyodont i.e., their teeth are continuously shed and replaced during the existence of the animal. It is estimated that one crocodile may replace each of its 80 tooth about 50 times throughout its lifespan. Humans however, are diphyodont, meaning that they can grow only two successive sets of teeth within their lifetime: the deciduous (milk) teeth, which are followed by the permanent (adult) teeth. After that they lose their ability for tooth renewal.
The present study observed that each tooth of an alligator behaves like a complex ‘family unit’. Each of these units comprises of a functional tooth which is the most mature tooth, a successional tooth that will later be developed in to a functional tooth and the dental lamina. These components were found to be at different stages of development. Furthermore, the researchers were able to identify a type of cells in the dental lamina of the alligators which they suspect to be dormant teeth stem cells that can be activated when a functional tooth is shed or extracted.
The research also provides information about the signalling molecules that plays a critical role in tooth development and renewal of the alligators.
Humans may have the potential for tooth regeneration
Dental lamina, the source of odontogenic stem cells for cyclic tooth regeneration, usually begins to degrade in humans after the generation of secondary tooth. Thus the humans lose the ability of regenerating their adult teeth. However, a remnant of it still exists and may initiate odontogenic tumors later in life. Previous literature reveals the presence of teeth stem cells in adult humans. Although these cells retain the ability of differentiation, they cannot generate a whole new tooth.
the following video can provide a basic idea of human tooth development.
No more dentures!
Tooth loss is a common problem that may occur due to various reasons including fractures, physical injuries, tooth decay and infections of the gum. Though this condition is rarely critical, it often results in aesthetic and psychological concerns thus necessitating in replacement of tooth.
Current options available for tooth replacement include techniques such as dental implants made out of biocompatible materials like titanium that can be inserted in the teeth bone. However the success of these implants is not completely satisfactory in terms of their performance and long-term stability. Therefore, many recent researchers focus on the potential of odontogenic stem cells to grow living tooth with proper functional characteristics. Several studies report regeneration of teeth using stem cells in vitro, although their use in dental practice is still challenging owing to factors such as high risk of rejection.
The current research however, promises of a future potential of regeneration of teeth in vivo. These findings suggest the possibility of using this knowledge for stimulating the dormant stem cells present in the remnant human dental lamina to initiate tooth regeneration process. In addition, the researchers hope that this will help in treating oral diseased that involve supernumery teeth formation.
Wu, P., Wu, X., Jiang, T. X., Elsey, R. M., Temple, B. L., Divers, S. J., ... & Chuong, C. M. (2013). Specialized stem cell niche enables repetitive renewal of alligator teeth. Proceedings of the National Academy of Sciences.